Hero the Cow was found frozen to a field in Virginia last April. He lost two of his hooves due to frost bite.

The plucky little calf would normally have been euthanised, but thanks to the Texas A&M College of Veterinary Medicine he's now walking with a pair of prosthetic limbs.

Ashlee Watts is an assistant professor at Texas A&M and says Hero's the first large animal they've put two prosthetic legs on. She hopes Hero will be able to work with wounded warriors and children with special needs.

But Monday Tripod ended up stranded and sinking between chunks of ice in the middle of frozen Byrd Lake in the Cumberland Mountain State Park.

Using a pick ax rangers pulled a boat over the ice, clearing a path for the animal to swim back to shore.

As soon as she was able to touch solid ground, they say the deer succumbed to exhaustion. Rescuers hauled her out of the water and over to a ranger's nearby house where they let her rest in a vacant dog pen, covered in blankets and straw.